Don't Mess With My Sister
by a.m567
Summary: Have you ever wondered what happened between Caleb and Tobias when they met that day in Amity headquarters? What did they talk about? Here's the full story. Shockingly, this is the first one there is on this subject.
1. Chapter 1

Okay, so here it is. The idea came to me, and I really wanted to write about it. I think it's pretty good, but of course, I want you to tell me what you think. R&R. And check out my other stories, I think they're worth reading. - a.m567

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**(Tobias's POV)**

I was lying on my bed, wondering how long we'll be able to last without allowing the natural Dauntless tendencies to creep in, when I heard a knock on my door.

I was surprised to find Caleb, who is probably one of the least likely people to come knocking on my door. I really don't know what to think of the guy. He's Tris's brother, so I kind of have to like him, but I don't know if I do. I don't know much about him, but I can tell that he could definitely fit in with Erudite. Which makes sense, since he chose those traitors in the first place. Tris doesn't exactly talk about him much, so I have no idea what to think.

I look at him, waiting him to say something. I'm not at all sure what he wants. We don't talk a lot, and after our little exchange before our hearing with the Amity, I'm not sure he likes me very much.

He nods his head in response. "Four," he says my name stiffly, as if he's unsure if that's what he should call me. "This is about Tris," he says abruptly, and realization dawns on me. He wants to have the whole 'be good to my sister' talk.

"Look, Caleb, I—"

"No, it's alright. I'm just, you know, a bit curious and all, and well... I was wondering if you'd mind talking to me about it, because I really care about her."

Oh god. I really don't need a 'stay away from my sister' lecture. But what am I supposed to do about it? 'No, sorry, I don't want to talk about my relationship with your sister, so hell if you don't know anything about me. Now leave.'

I can't do that, even if I want to. Tris wouldn't forgive me if I didn't at least try to make peace with her brother. He_ is_ the only family she has left.

I sigh. "I guess you should come in, then. I doubt you want to talk in the hallway," I say tiredly. I don't feel I need to be warm or hospitable. I'm sure Tris wouldn't want me to act differently around Caleb, which is fine by me. I don't have to and don't exactly want to impress him.

He shuffles awkwardly into my room, and I hesitate before shutting the door behind him. He looks uncomfortably around the room, hands in his pockets, rocking on the soles of his feet.

I look at him stoically, wondering how in the world this is going to go. He looks at the bed, as if wondering if there is a place to sit, but for some reason, we both end up sitting on the floor.

"So, how long have you and Tris been… together?" he asks, jumping straight to the point. I think about it before answering.

"Just over half way through initiation?" I guess. It sounds about right. It was right after stage two.

"Since you're two years older than her," he starts, and I can hear the spite in his voice, "you couldn't have been in the same initiation as her. How did you guys meet?"

I stare at the floor beside him. I'm not sure how he'll take it if he finds out I was her instructor. I don't think he'll be too happy about it, that's for sure.

"I was her instructor through initiation," I say, mainly to see his reaction, because I know he won't just take it plainly. I see his eyes go wide.

"Her instructor?" he asks. "Isn't that a little… inappropriate?"

I just shrug. "It doesn't really matter now, now does it?" I see his face grow a soft shade of red and his eyes flash with irritation.

"You don't talk a lot, do you, Four?" he asks angrily, struggling to calm his nerves. He fails miserably, especially when all I do is chuckle in response.

"Depends what I'm talking about, or who I'm talking to," I say, even though I know I'm not appealing to his good side.

"Well, seeing as we're talking about my _sister_, the girl who you so happen to be _dating_, I would think you'd care a little more." As he speaks, can see the frustration rack his body. In a way, he's right. Since I'm having this conversation, I might as well finish it and at least make him not hate me. And now he thinks I don't care about Tris, which is biggest lie I've ever heard.

He mumbles something, just loud enough for me to hear. "I knew you were just messing around with her."

That is enough to make me snap back to at least a half-caring state. I am _not_ messing around. Absolutely not. I love her.

I might not admit it often, even to myself, but I do love her. I have for a while. It's just something about her… I don't know. Maybe it's the way she is so brave and determined. Or the way no one thinks she's capable of anything and she does whatever she can to prove them wrong. Maybe it's the fact that she's so selfless and brave and powerful and she doesn't think so. And the fact that even though she is so adamantly against it, she is beautiful. I know most guys wouldn't think so, but I do. The way her hair is so soft and blond and her eyes are so blue and sparkling and full of determination. They have the power to break me to pieces, those eyes. She's the only thing that has managed to penetrate the layer of hard, cold harshness that I have let cover me. It's something that constantly puzzles me; how did she do it?

After Marcus, I created that hard layer to protect myself from the world, and she just arrives and melts it away. I care about her a lot, more than I'd care to admit. And I'm so afraid that after I've let her in; the only person I have let in, that she will leave me shattered beyond repair. I haven't given anyone this kind of access to me before, and even though I know she won't abuse it, I can't help but worry she will. I feel so… _vulnerable_ when I'm around her, like she knows all my weaknesses and can exploit them whenever; like she has the power to destroy me then and there. Which she does. And it terrifies me.

My expression hardens. "I'm not messing around. I care about her, Caleb. I'm not going to hurt her." The tenderness in my own voice surprises me. I can tell it surprises him too, because he softens his expression just a bit. I can tell that he's not 100% sold, though.

"Okay," he says skeptically, stretching out the word as if not sure he really wants to say it. "But we're not done yet," he adds hurriedly.

_Of course we're not._ I sigh. What else does he want?

"What else do you want me to say?" I ask.

He looks me hard in the eyes. "You better not be messing around with my sister. _Especially_ because you're older than her, and…" he trails of, but I know what he means to say. Don't make her do anything she doesn't want to do, don't be a jerk, etc, etc. I get it.

"I'm not a jerk, Caleb. I'm not going to force her into anything, if that's what you're worried about." The statement doesn't affect me. So what if he wants to give me 'the talk'. It will probably embarrass him more than it will me.

He just nods. "So… how did you end up together? You were her instructor, right? How did that just… happen?"

I sigh. "I guess we kind of… I don't know. I guess I started to like her, and I knew she liked me back, and…." I trail off. I can tell he isn't satisfied with the answer, but that's all he's going to get. I'm not even sure how it happened in the first place. I'm not going to tell him about the many things that have got us together over the course of initiation; I'm confused about it myself.

I remember the things we'd done together before the war. I remember her jumping first; that grey blur that captured my heart the first time she grabbed my hand at the net. I picture the time she saw me drunk by the chasm. I remember when she was so smart and brave and stupid when she climbed the Ferris wheel during capture the flag, and how determined she was. I can't stop myself from smiling and chuckling when I remember her stubbor face when I threw knives at her while she protected her friend. I try not to think about the fact that that friend betrayed her and almost killed her with a bunch of other lunatics.

Snapping back to reality, I notice Caleb frowning at me, probably wondering why I just chuckled.

"What's so funny?" he asks, as if I'm keeping back a joke and he's very offended by it.

"I was just thinking about initiation. She was… quite determined." I'm not sure if telling him that I throw knives at her head is a good idea.

"What did you guys have to do for initiation? I've always wondered what Tris had to do to become… Dauntless." I frown. Was that supposed to be an insult? To Tris, or to Dauntless?

He seems to read my thoughts and talks hurriedly. "I mean, not that there's anything wrong with being Dauntless or anything," he says quickly, and I chuckle at his nerves.

"Well, Dauntless initiation consist of three stages- physical, emotional, and mental. At the end of initiation, only the top ten initiates from Dauntless-born and transfers alike get to stay in Dauntless."

He takes in the information. "What did my sister rank?" he asks after considering his question for a bit.

I smirk. "First."

A look of surprise crosses his face, and it makes me annoyed. How come nobody thinks she's capable of anything? "You shouldn't look so surprised," I say hardly. "She's a lot more capable than everyone gives her credit for."

"It's not that, it just…" he sighs. I'm not sure what he's getting at, but seeing the sad look on his face, I soften. I remember that he lost his parents as well, not just Tris. And he's not much older than her, too; it must be hard on him.

"Stage two and three are what challenges most initiates. In stage two, they have to face their fears by going into a fear simulation that shows them their fears. They have to calm their heart rate or stop panicking enough in order to get out. In stage three, they go through their fear landscape. This puts them up against all their fears at once and they have to do get out of them all. The difference is that in stage three, they are aware in the stimulation and in stage two, they aren't." I stiffen a bit. I was going to mention that Tris was actually aware during stage two as well, but I don't know if I should. I'm not sure if she's told him about her Divergence yet. So instead, I keep my mouth shut.

I can almost see the gears turning in his head as he greedily digests the new information. His eyes glisten with curiosity and his interest in the topic. Erudite at heart, all right.

"What about the first stage?" he asks eagerly, craving the new information.

"In stage one, they learn how to fight, shoot guns, and throw knives."

His eyes widen. "Are you serious? You guys throw _knives_?"

I find myself smiling at his shock. "Yup. We're actually pretty good at it, too." He shakes his head in disbelief.

I get up, walk over to the small shelf beside my bed and take the knife that lies there.

"What are you doing?" he asks carefully, voice full of curiosity and tinged with worry. Instead of answering, I bring the knife over and sit next to him again.

"I'll show you our knife throwing if you don't believe me." He looks at me worriedly, indecision flashing across his features. "Don't worry," I say, rolling my eyes. "I'm not that bad," I say, hiding a grin. I'm also extremely modest.

"Give me something to aim at," I challenge.

He looks at me decidedly. "Okay," he says slowly, choosing to trust me. He looks around the room for a target, his eyes resting on the block of cheese sitting on top of the dresser. "That hunk of cheese, right on top of the shelf," he says pointing. I smile. Easy as cake. Dauntless chocolate, of course.

I breathe and get into stance without even paying attention to my actions. I've done this so many times it's almost second nature. I'm not sure this should worry me, but seconds later I see the knife stick out from the cheese and smile triumphantly. "And that was while sitting down."

He stares at me open mouthed, then fixes his eyes determinedly at goes to get the knife, struggling to wedge it out of the block. When he does, he stands next to where I'm sitting. "It can't be that hard," he says. I just look at him bemusedly. Of course it's not.

He aims for the cheese, his footing wrong and his breaths clumsy. He releases it fumblingly and it flies choppily in the air, only hitting the wood of the shelf a foot away from the top.

I stifle at laugh at his dejected face. He looks at me and scowls. "Do it again," he orders, probably wanting to see my technique He passes me the knife, taking a seat to watch me closely. I effortlessly launch the knife into the air, watching it sink seamlessly into the cheese.

He just shakes his head in disbelief, a look of wonder on his face. He goes again to retrieve the knife, determinedly taking a place on the floor beside me. He tries to imitate me, failing miserably and ending up with the knife at the foot of the dresser, embedded in the floor. This time, I can't stop myself from laughing. I end up clutching my chest, my laughter fueled by the look of irritation and embarrassment on his face.

"No, not like _that,_" I say through laughter.

"What do you mean, 'not like that'?" he says incredulously. "I imitated you perfectly!"

"You did not," I say vehemently.

"Well, do it again, then," he orders challengingly.

Suddenly, the door opens, revealing Tris in the doorway. Caleb and I avert our attention to her. After all, she's the reason this conversation started in the first place.

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There's this really nice box that you write thing in that makes the author very happy. Use it.

(Please?)


	2. Disclaimer

**Disclaimer:**

**I do not own any of the characters or settings in this entire FanFiction that I have written. They all belong to Veronica Roth and I own nothing. I am not making any profit on the making or publishing of this story, and it is strictly for entertainment purposes.**


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